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The earliest evidence for life on Earth includes: 3.8 billion-year-old biogenic hematite in a banded iron formation of the Nuvvuagittuq Greenstone Belt in Canada; [30] graphite in 3.7 billion-year-old metasedimentary rocks in western Greenland; [31] and microbial mat fossils in 3.48 billion-year-old sandstone in Western Australia. [32] [33 ...
The history of life on Earth traces the processes by which living and extinct organisms evolved, from the earliest emergence of life to the present day. Earth formed about 4.5 billion years ago (abbreviated as Ga, for gigaannum) and evidence suggests that life emerged prior to 3.7 Ga. [1] [2] [3] The similarities among all known present-day species indicate that they have diverged through the ...
Population estimates cannot be considered accurate to more than two decimal digits; for example, the world population for the year 2012 was estimated at 7.02, 7.06, and 7.08 billion by the United States Census Bureau, the Population Reference Bureau, and the United Nations Department of Economic and Social Affairs, respectively, corresponding ...
Lungs and thin, moist skin allowed them to breathe; water was also needed to give birth to shell-less eggs and for early development. Dorsal, anal and tail fins all disappeared. Lissamphibia (extant amphibians) retain many features of early amphibians but they have only four digits (caecilians have none). 330-300 Ma Hylonomus
The universe has appeared much the same as it does now, for many billions of years. It will continue to look similar for many more billions of years into the future. The galactic disk of the Milky Way is estimated to have been formed 8.8 ± 1.7 billion years ago but only the age of the Sun, 4.567 billion years, is known precisely. [82]
The Day of Five Billion, 11 July 1987, was designated by the United Nations Population Fund as the approximate day on which the world population reached five billion. Matej Gašpar from Zagreb , Croatia (then SR Croatia , SFR Yugoslavia ), was chosen as the symbolic 5-billionth person alive on Earth .
Stars are known to get brighter as they age, and the Sun has become 30% brighter since its formation 4.5 billion years ago. [70] Many models indicate that the early Earth should have been covered in ice. [71] [66] A likely solution is that there was enough carbon dioxide and methane to produce a greenhouse effect. The carbon dioxide would have ...
The timeline of the universe begins with the Big Bang, 13.799 ± 0.021 billion years ago, [1] and follows the formation and subsequent evolution of the Universe up to the present day. Each era or age of the universe begins with an " epoch ," a time of significant change.